32 bit ACES to srgb web

[Tsiky]

Hello guys! 

I know this has been asked several times here but unfortunately I couldn't find a clear answer.

My goal is to display my ACESCG render correctly and export it to web as JPG

- Right now the preview in the OCIO display transform is the correct look, but I know it won't look correct when I export it.

- So I am trying to replicate that look with ICC display transform. What I am trying to avoid is to use manual adjustments like levels, curves, etc. The closest I've got was using OCIO node but still looks washed off and less contrasty.

Am I missing something here?

Thanks!

[walt.farrell]

Have you watched the official Affinity OCIO-related tutorials? If not, they might help.

https://affinity.serif.com/en-us/tutorials/photo/desktop/video/297059572/

https://affinity.serif.com/en-us/tutorials/photo/desktop/video/441014543/

 

[Tsiky]

Yes I have watched those video, and they were helpful. However it can't find the thing that I am looking for.

As far as I know, the OCIO display transform does 3 things:

1. Convert ACEScg to linear srgb
2. Tonemap the linear srgb (RRT)
3. Add view transform for monitor (ODT)

The ICC display only enables me to do 1 and 3. How do I get the tonemapping coming from ACES? 

[kirkt]

Take a look a this tutorial by James Ritson:

- although it is about using OCIO and LUTs in the context of Blender filmic tone mapping, it is probably directly relevant to what you are trying to do.  Note in the video that you must enable ICC Display Transform in the Preview panel to get the transforms you apply in your layer stack to render the gamma-encoded output correctly to the output file (this is covered at about 9:00 in the video).

kirk

[kirkt]

@Tsiky - Here is an example, using the ACES command line utility called rawtoaces to make an ACES EXR file - rawtoaces converts a raw camera image file (like a .CR2 or .NEF file) to an ACEScg linear EXR file.  The actual raw file I converted is an HDR raw file created with some interesting computational merging techniques similar to the Adobe Camera Raw HDR DNG.  In other words, it is a true HDR file, not just an EXR made from one raw exposure.

see: https://github.com/ampas/rawtoaces for more info on rawtoaces.

In this example, I simply opened the EXR file that comes out of rawtoaces in AP - in my Preferences, I have designated ACEScg as my 32bit working color space in AP, and sRGB as my RGB working color space.

I added an Exposure adjustment layer to adjust the unbounded exposure of the data prior to the OCIO transform.  I also added a Curves adjustment layer to adjust the White Balance - if you simply drag the highlight end of a channel's curve downward, it is like decreasing the exposure of that channel - the curve just has to remain linear in shape (no other adjustment points on the curve except for the two endpoints) for it to act like an exposure adjustment - at least this is how Photoshop works.  Then I applied the OCIO transform of ACEScg to sRGB.  This tone maps the image using the ACEScg to sRGB transform.  

Now the file's numbers are in sRGB.  

To get things to output properly to gamma-encoded output like a JPEG you need to do two things:

1) The working RGB color space specified in your preferences needs to be sRGB.

2) The 32bit Preview panel's Display Transform needs to be set to ICC Display Transform.

Now, when you export the JPEG, it will be in sRGB (the JPEG is written to the working RGB color space) and it will look like the preview that you see when you enable the ICC Display Transform.

This is essentially what the video to which I linked specifies near then end.  In the attached screenshot, the EXR displayed as a Preview is on the left, the output file, opened in AP is on the right.  Note that it appears as if there is a very slight shift in the black point in the JPEG, but it is otherwise pretty much the same as the Preview - examine/compare your output at 100% to see if this is a real shift, or just a Preview rendering issue - in my output, the files look identical at 100% zoom.  

 

Kirk

[kirkt]

Can you post a link (Dropbox, etc) to one of your EXRs so we can try to replicate your issues?

kirk

[Tsiky]

 Kirkt,

Yup you explained exactly my issue. I don't think it's an issue anymore, but I'll share here what I've learned through your answers and a few searches. For ACES to work properly, I need to work with ICC display transform (in my case srgb), convert from Acescg to srgb (linear) using OCIO, then manually tonemap it using curves. I was trying to avoid using luts or curves for tonemapping, but that's exactly what it needs. I just wish AP had an easier way to do it. Like in Davinci Resolve you just set your working color space, set the IDT and ODT and you are done

Here's the exr file if you still want to take a peek: https://drive.google.com/file/d/1m5MC9O7JMjB3UKLCSgIAwKoA9v84UuWe/view?usp=sharing

 

 

[johncido]

After check out the video in kirkt's answer, I came up with this setup to export ACEScg as sRGB png.

First, set it to ICC display transform:

Then create these two OCIO layers:

This is the 'to Linear' layer:

This is the 'to sRGB' layer:

And this is the comparison (Blender exported PNG on the left, AP exported PNG on the right):

Could use some further tweaks, but it seems working for me now.

[Tsiky]

On 10/13/2021 at 10:47 AM, johncido said:

After check out the video in kirkt's answer, I came up with this setup to export ACEScg as sRGB png.

First, set it to ICC display transform:

Then create these two OCIO layers:

This is the 'to Linear' layer:

This is the 'to sRGB' layer:

And this is the comparison (Blender exported PNG on the left, AP exported PNG on the right):

Could use some further tweaks, but it seems working for me now.

This worked like a charm! Thank you so much

[Thomas Helzle]

Thanks a ton johncido!
I thought I tried everything but couldn't get the export from ACEScg EXRs to jpg or png to work.
I'm using Octane for rendering in SideFX Houdini and so far used Fusion to convert ACEScg EXRs to 16 bit PNGs for further editing in AP for the web.

Your solution is much faster, but I still think Affinity Photo (v2 in my case) should allow to export what it shows in the viewport without this workaround.

With the 32 bit preview set to OCIO, sRGB and ACES (using ACES 1.2 globally here) I get a perfect match with the Octane preview in the viewport, but so far wasn't able to export anything usable.
There should definitely be an option to "bake" what the 32bit preview shows to a 8 or 16 bit image and also have the export dialogue have an option to export what I see on the monitor.
The current system feels somehow half baked in that regard - what else would I want for export/convert to such formats than what I see on the screen...?

Come on Affinity, you can do better than that!

Cheers and thanks again johncido,

Tom